You have to be careful listening to “The Money Masters”, since it’s a mix of truth and completely wrong and misguided economic policies.
What’s correct about that “documentary” is that fractional reserve banking enrich the few at the expense of the many.
What’s wrong is almost everything else.
They fail to understand a basic economic law, which is that the size of money supply doesn’t matter, any size is optimum for the economy to function properly.
They beleive that increasing the supply of money causes prosperity, and the only thing wrong about it is that it enriches private indivudual. Same for the FED. What they critisize is not that it exploits the poor, but that it enriches private banks and that it’s “secret”. What they promote is a FED but totally controlled and run by politicians and bureaucrats.
There’s so many things that are wrong in the documentary that it makes an uninform public know even less about sound economics than before he watched it. For instance, tally sticks were not money, they were mostly bonds certificates. They were not even homegenous goods. Continental scripts didn’t create prosperity, they were all inflated out of existance. Ben Franklin was pro-fiat money because he owned a printing press (literally) and had government contracts to print the money himself.
The whole documentary is a primitivo-socialist rant against what is “private”, “secret”, and glorifies the government. They promote a masively inflationary government managed money, without realizing that it’s exactly what we have now.
To answer your specific question, I seriously doubt that “70% of the gold supply” is in the hand of a small group of people. Rich people don’t hold they wealth in gold, they hold land or financial assets. Central banks hold about 12-18% world money supply, depending of the source, and that’s already a huge part.
But anyhow, it wouldn’t matter, since money holdings represent always a very small part of the total wealth in an economy, and for it to confer any advantage to their holders, they have to spend it.